docs: def calculate_content_width(self):
          """
          Calculate the width of inner content of the border.  This will be the width of the menu borders,
          minus the left and right padding, and minus the two vertical border characters.
          For example, given a border width of 77, with left and right margins each set to 2, the content
          width would be 71 (77 - 2 - 2 - 2 = 71).
  
          Returns:
              int: the inner content width in columns.
          """
          return self.calculate_border_width() - self.padding.left - self.padding.right - 2